Severe delayed post-polypectomy induced ulcer (PPIU) bleeding is a common problem with increased numbers of colonoscopies being performed and with more patients taking anti-coagulants or anti-platelet drugs. Current medical guidelines are not effective for prevention of delayed bleeding nor is empiric closure of PPIU's with clips because the underlying artery is still patent in the ulcer base as shown by our recent Doppler endoscopic probe (DEP) studies. Specific Aims: The primary aim is to perform a randomized controlled trial (RCT) to compare rates of delayed hemorrhage after DEP detection of arterial blood flow and focal treatment in PPIU's (treatment arm) with standard treatment using medical guidelines alone (controls) for prevention of delayed bleeding in high risk patients after snare resection of benign colon polyps. Secondary specific aims are quantitate hospitalization rates and hospital days for delayed PPIU bleeding and study the natural history and risk factors. Methods: This is a RCT performed by the CURE Hemostasis Research Group for high risk patients - those with PPIU's 15 mm in size with or without drugs associated with bleeding; or patients who require anti-coagulants or anti-platelet drugs and have PPIU's 10 mm or larger. Outpatients, scheduled for screening or surveillance colonoscopies, who give written informed consent and meet entry criteria will be randomized to control/no DEP (medical treatment without PPIU closure) or DEP (as a guide to arterial blood flow detection and focal obliteration of it with hemoclips and/or low power MPEC probe). Patients will be prospectively followed at 7, 14, and 30 days for bleeding, hospitalization complications, or unscheduled visits for healthcare after polypectomies. Data will be prospectively collected, checked for completeness, de-identified, entered onto data files, and managed with SAS. Univariable and multivariable analyses will be performed to evaluate the clinical, endoscopic, and blood flow risk factors for delayed PPIU hemorrhage. Based upon recent results, our sample size estimate is for 330 patients, 165 in each treatment group. With the numbers of colonoscopies done here for screening surveillance, abdominal pain, or change in bowel habits in high risk patients and the referral of large polyps for removal, we anticipate completion of enrollment and follow-up in 4 1/2 years and the RCT in 5 years. To increase the generalizability of results to the US population and the scientific scope, we plan to enroll patients at both WLA VA medical center (primary center) and additional Veterans and many more females in a secondary center - UCLA which is a closely affiliated, university medical center where the investigators also attend.